Evaporative cooling equipment dissipates heat by evaporation of the re-circulating cooling water. As the re-circulating cooling water evaporates, the concentration of any dissolved minerals in the re-circulating cooling water increases which can result in scaling and corrosion of the evaporative cooling equipment.
As is commonly known in the art, once the mineral buildup reaches a pre-determined threshold level, the mineral-laden re-circulating cooling water is then bled, commonly known as “blow-down”, from the evaporative cooling equipment and replaced with make-up water that contains a lower concentration of minerals. Conductivity of the re-circulating cooling water is sometimes measured to reflect the mineral content thereof. When the mineral buildup reaches the threshold level thereby raising the conductivity to a threshold amount, a blow-down valve is activated in order to replace the mineral-laden re-circulating cooling water with make-up water to lower the concentration of the dissolved minerals in the re-circulating cooling water.
Blow-down of the evaporative cooling equipment occurs as follows: When the mineral content of the re-circulating cooling water, and hence the conductivity of the re-circulating cooling water, reaches a pre-determined threshold level, a controller reading the threshold amount of conductivity sends a signal to open the blow-down valve thereby directing the mineral-laden re-circulating cooling water to drain away from the evaporative cooling equipment. As the re-circulating cooling water volume drops, make-up water is automatically added thereto. Since the make-up water contains less minerals than the re-circulating cooling water, dilution of the concentration of the dissolved minerals in the re-circulating cooling water occurs thereby causing the conductivity of the re-circulating cooling water to be lowered below the threshold amount of conductivity. When the threshold amount of conductivity is achieved, the blow-down valve closes. Thus, the mineral concentration of the re-circulating cooling water remains within a predetermined range that is acceptable for operating the evaporative cooling equipment.
A prior art sampling and blow-down arrangement for evaporative cooling equipment is illustrated in FIG. 1. In a diagrammatical scheme, an evaporative cooling system 110 re-circulates cooling water through a cooling tower 112 via a pump 114 interconnecting an upstream conduit 116 as a source of the cooling water to the pump 114 from the cooling tower 112 and a downstream conduit 118 to pump the cooling water to the cooling tower 112. A sampling circuit 120 interconnects the upstream conduit 116 and the downstream conduit 118 so that a sample of the re-circulating cooling water can be diverted therethrough. The sampling circuit 120 includes an upstream shut-off valve 124 disposed adjacent to conduit 118, a downstream shut-off valve 122 disposed adjacent to conduit 116, a conductivity sensor 126 disposed between the upstream shut-off valve 122 and the downstream shut-off valve 124, a flow switch 128 disposed between the upstream shut-off valve 122 and the conductivity sensor 126 and a ‘Y’ strainer 130 disposed between the conductivity sensor 126 and the downstream shut-off valve 124. A bleed line 132 having a blow-down valve 134 is connected to the downstream conduit 118 and is disposed between a drain 135 and the downstream conduit 118. A make-up water source 136 is disposed upstream of the pump 114 by way of example only. A controller 138 reads the conductivity signal from the conductivity sensor 126 and the flow switch 128, then appropriately operates the blow-down valve 134. The make-up water source 136 operates off a float or other method to detect low water level. This combination of components will maintain a desired range of conductivity of the cooling water as is well known in the art.
Another prior art sampling and blow-down arrangement for evaporative cooling equipment is illustrated in FIG. 2. This prior art sampling and blow-down arrangement is similar to the one illustrated in FIG. 1 except where the bleed line 132 and associated blow-down valve 134 are located. In this diagrammatical scheme of FIG. 2, the bleed line 132 and the associated blow-down valve 134 are connected between the upstream shut-off valve 122 and the flow switch 128. Otherwise, this prior art sampling and blow-down arrangement operates as the one in FIG. 1.
Although each one of the prior art sampling and blow-down arrangements for evaporative cooling equipment is effective, there is a drawback, particularly in freezing, or potentially freezing, environments. The sampling circuit 120, the bleed line 132 and the blow-down valve 134 must be heated and insulated to prevent freezing.